Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.29	9.871%	$192.5929	$192.59	$192.60	$192.60
Purchase #2	$202.59	13.156%	$229.2427	$229.24	$229.25	$229.20
Purchase #3	$12.97	7.416%	$13.9319	$13.93	$13.95	$13.90
Purchase #4	$12.29	4.620%	$12.8578	$12.86	$12.85	$12.90
Purchase #5	$124.80	11.666%	$139.3592	$139.36	$139.35	$139.40
Purchase #6	$55.31	7.806%	$59.6275	$59.63	$59.65	$59.60
Purchase #7	$75.85	3.212%	$78.2863	$78.29	$78.30	$78.30
7 purchase totals =	$659.10		$725.8983	$725.90	$725.95	$725.90